INFLUENCE OF THE MODES OF HEAT TREATMENT ON THE STRENGTH AND CYCLIC CRACK-GROWTH RESISTANCE OF 65G STEEL

摘要

To find the ways of increasing the brittle-fracture resistance of the metal in the heat-affected zone formed as a result of repair surfacing of the rolling surface of railroad wheels, we study the influence of various modes of heat treatment, including the traditional and modified (by the authors) Q-n-P-treatments on the mechanical properties of 65G steel regarded as a model wheel steel. It is shown that, after the modified Q-n-P-treatment, the mechanical characteristics of steel increase to a greater extent than after the traditional treatment. However, according to the parameter of structural strength P = [Delta U . Delta K-th . Delta K-fc], where Delta U is the ultimate strength, Delta K-th is the fatigue threshold, and Delta K-fc is the cyclic fracture toughness of the material, the mode of treatment proposed earlier, which leads to the relaxation of stresses of the second kind in the bulk of martensite and bainite lathes, proves to be more efficient.